A device for contactless optical distance measurement is, for example, described in Document DE 10 2006 017 400 A1 (U.S. counterpart application published as 2007/242279). The device has a measurement head with an imaging optical system with chromatic aberration. Through the optical system is imaged a light exit surface of a light source in wavelength-dependent focal planes and there generates a measurement spot of, for example, a few micrometers in diameter, in the region of which an object to be measured can be located. The light back-reflected by the object passes through the optical system in the reverse direction and is, for example, coupled into a fiber end, through which the light has entered the measurement head. A sharp image of the light exit surface of the light source, for example of a fiber end face, onto the object to be measured and vice versa ensues in each case on the basis of the chromatic aberration of the optical system only for a specific wavelength λ. In a spectral analysis of the reflecting light the wavelength λ thus shows a sharp peak, from the wavelength of which the distance between the measurement head and the object to be measured can be determined via a calibration.
An optical distance sensor, which is based on this principle of the confocal imaging via a lens system with chromatic aberration, is known from Document US 2008/0239278 A1, for example.
The devices for contactless optical distance measurement known from prior art typically have at least three or four lenses, in order to generate a measurement region predetermined by the chromatic aberration of the lens system.